Banjo simulation system

ABSTRACT

An array of tone signal sources is connectable to a common collector via key switches. The common collector leads to parallel percussive gating paths, normally nonconductive, which are turned on simultaneously in response to depression of any key regardless of the condition of other keys, and which become nonconductive gradually at diverse rates following the depression whether or not the key is released.

United States Patent 3,407,260 10/1968 Schrecongost Inventor David A. Bunger Cincinnati, Ohio 768,069

Oct. 16, 1968 Feb. 23, 1971 D. H. Baldwin Company Cincinnati, Ohio Appl. No. Filed Patented Assignee BANJO SIMULATION SYSTEM 15 Claims, 1 Drawing Fig.

U.S. Cl 84/1.26 Int. Cl GlOh l/02 Field of Search 84/1.01

References Cited UNITED STATES PATENTS Hadden 3,470,306 9/1969 84/1.19 3,476,864 11/1969 Munch et al.... 84/1.24X 3,480,718 11/1969 Hohls et a1 84/1.01 3,484,529 12/1969 Moore 84/1 .01

Primary Examiner-W. E. Ray Assistant Examiner-Stanley J. Witkowski Attorneys-W. H. Breunig and Hurvitz, Rose & Greene ABSTRACT: An array of tone signal sources is connectable to a common collector via key switches. The common collector leads to parallel percussive gating paths, normally nonconductive, which are turned on simultaneously in response to depression of any key regardless of the condition of other keys, and which become nonconductive gradually at diverse rates following the depression whether or not the key is released.

PATENTED FEB 2 3 I97! m? is ATTORNEY l BANJO SIMULATION SYSTEM BACKGROUND OF THE'INVENTION Musical interests exists in simulatin'g percussive string instruments in electronic organs, without requiring skilled manipulation of keys to produce strumming effects. Percussive gates are well known, and it is known to produce musical effects responsive to plural then-depressed keys of an organ,

on depression of another key. The present system passes tone signal through parallel gates which are noncoincident in time, and which preferably carry tones of diverse tone colors. This simulates strumming. To simplify playing, a chord is percussively heard corresponding with all depressed keys, whenever even one key is depressed.

SUMMARY on THE INVENTION An organ arranged for simulating banjo tones by passing a called-for chord of tone signals through diversely timed. percussive gates whenever one key of the organ is depressed.

BRIEF DESCRIPTION OF THE DRAWINGS The single FIG. of the drawing is a schematic circuit diagram of a system according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS which the sources 10, 11, 12 are connected, respectively, via

key switches 8,, S S and isolating resistances 15, 16, 17 to a common lead 18. The lead 18 diverges in two paths l9 and 20. In path 19 is included an emitterfollower active filter 22 employing an NPN transistor T,, which supplies signal via a high pass filter 23 peaking at (C to the drain electrode of FET F,, the source electrode of which is connected via isolating resistance 24 to a terminal 25. Terminal 25 leads via a tab switch S, to an amplifier 26 and loudspeaker 27. Path 20 leads via high pass filter 30 to the drain-electrode of PET F,, the source electrode of which isconnected via isolating resistance 31 to terminal 25. Resistance 32 is connected from terminal 25 to ground, and represents a load across which voltage is developed for application to the input of amplifier 26.

When any keys are depressed, corresponding ones of switches 8,, 8,, S, are also closed, but switch S, and S, are commonly operated, as are S,,, 8,? and'S 8,, etc. A DC header 90 in which voltage from terminal 40, at l v. is then applied, for each switch, via a separate large resistance (lm), typically 41 for the switch 8,, 42 for the switch S and so on, which causes current to flow in resistances 43,44, in series, the latter being connected to ground. The total current flowing in resistance 44, and therefore the total voltage thereacross, is a function of the number of switches 8,, S

. which may be closed. Voltage transients across resistance 44 are transferred via capacitor 45 to-thebase of NPN transistor T,. The emitter of T, is grounded, and it is collector loaded by resistance 46. Its collector is capacitively coupled through capacitor 47 and a resistive divider network composed of resistances 48, 49, to the base of NPN transistor. T,, which is emitter grounded and collector loaded by resistance 54. A direct connection 51 exists between the. collector of T, and the base of T,, through resistance 52.

T2 is normally nonconductive, which maintains T, conductive through feedback connection resistor 52. If T, becomes nonconductive in response to a negative signal, it turns T, on.

When a negative voltage arrives across resistance 44, on closure of one of switches 8,, 5,, etc, and this can occur regardless of whether or not others of the switches are then closed, a negative pulse is transmitted through capacitor 45, turning T, off. This action transfers a positive pulse to the base of T,, rendering it conductive. T,

on, or conductive, because the collector of T, then provides a low resistance path to ground, so that the base of T, is essentially grounded. The design assures that if plural ones of switches 5,, 8,, etc., are closed almost, but not quite simultaneously, only one output pulse will nevertheless be derived from T,. This can occur due to imprecise playing.

When T is turned on, a negative pulse is applied to the base of PNP transistor T,, via capacitor 55, turning T,, on momentarily.

T,, is provided with collector voltage from tenninal 56 via a voltage divider composed of resistances 57, 58, having ajunction 59. This junction is normally negative, but when T, becomes conductive goes to nearly zero volts. A further voltage divider composed of resistances 60, 61 is connected between terminal 56 and ground, and provides a terminal 62. Terminal 62 is normally at l 2 v. and terminal 59 at -l 8 v.

The voltage at terminal 62 is applied to the gate electrodes of FETs F, and F maintaining these nonconductive. The connections are made via resistances R, and R respectively, and timing capacitors C, and C (.18 and .47), respectively, are connected between the gates and ground. The capacitors C, and C are, then, normally charged to l 2 v.

When T,, is transiently turned on, the gates of F, and F are grounded via D, and D through the collector of T,,. This occurs substantially instantaneously. When T, reduces to cutoff condition, C, and C, charge towards -l2 v. via R, and R respectively, i.e., audibly relatively slowly, and in due course F, and F will turn off. This turnoff occurs with an exponential characteristic. The time constant of R C is about 2.5 times the time constant of R,C,. The function of terminal 59 is solely to assure that D,, D, are biased off while T,, is nonconductive, since there may be leakage current in T,,, and the diodes D,, D, assure that capacitors C,, C, can discharge through a low resistance circuit and charge through another high resistance circuit as T turns on and off.

Filter 30 is a passive high pass filter, while amplifier 22 and associated components is an active high pass filter. Series capacitors 70, 71 act in series to discriminate against lows, and shunt capacitor 72 tends to bypass highs. T, is emitter loaded, and feeds back from the emitter via lead 73 to the base of T, via RC components R C, and C,R,,. These filters act to color tone, are per se well known, and other filters could well be substituted, so they have diverse characteristics suitable for the desired simulation of tone.

In operation, depression of one or more keys results in a transient turn-on of T,, which acts to rapidly turn on F, and F passing tone signal of two diverse colorations with instantaneous buildup. The struck tones thendie away, but at different rates, so that one is sustained beyond the other by about 2.5 times. Specific values of R,, R are selected according to the pinchofif characteristics of the FETs to provide a simulation of a banjo tone.

A percussive tone is sounded whenever a key is struck regardless of the length of time the key is held down, and if other keys are being held down when a key is struck, a percussive chord will be sounded in response to all the held down keys. It is within the scope of the invention to utilize more than two gates, if required to attain desired effects. To simulate a banjo, two gates are sufficient.

The time constant associated with F, is R,C,. R, is selected so that when F, is triggered it will remain on for approximately 30 ms. The active filter amociated with this gate is a high pass with a 12 db. peak at approximately 1 kc. The tone associated with this section tends to simulate the sound obtained from the drum head of the banjo when a string is plucked and is of short duration in nature.

The time constant associated with F, is R,C,. R, is selected so that when F, is triggered it will remain on for approximately 75 ms. The passive filter C R, associated with this gate is a remains off as long as T is 75 duration than the tone associated with the drum head. These relative values were derived by a listening test to determine which relationships best simulated the characteristic sound of said gate electrode and a point of reference potential;

means responsive to said transient pulse for rapidly I discharging said capacitor to said reference potential and thereafter for slowly charging said capacitor to said gating t g v said reference level being sufiiciently low to render said gate conductive; and

an acoustic transducer connected in cascade with said gate.

2. The combination according to'c'laim 1, wherein said percussive gate is a field effect transistor.

3. An electronic organ comprising:

plural sources of tone signals providing a gamut of tone signals arranged in frequency according to a musical scale;

a separate key switch connected in cascade with each of said sources;

a common collector connected in cascade with all said tone sources;

means responsive to closure of any of said key switches regardless of the then condition of the remainder of said key switches for generating a control pulse;

plural gates connected in parallel with each other to said common collector, said gates being normally nonconductive;

means responsive to said control pulse for rendering said gates rapidly conductive and thereafter relatively slowly conductive at audibly diverse rates for the separate gates; and

an acoustic transducer connected in cascade with said gates. v v

4. The combination according to claim 3, wherein is included a tone color filter in cascade with each of said gates, said tone color filters having diverse frequency response characteristics.

5. An electronic organ, including:

a source of tone signal;

a percussive gate connected with said source of tone signal;

a load for said gate, said gate including a gate electrode, a sustain capacitor connected between said gate electrode and a point of reference potential;-

a source of off gating voltage;

a resistive circuit connected between said source of voltage and said gate electrode, said capacitor and resistive circuit having an audibly evident time-constant;

a normally nonconductive switching transistor;

a normally nonconductive diode connecting said gate electrode to said transistor;

a source of control pulse connected in control relation to said switching transistor, said switching transistor arranged to be rendered conductive in response to said control pulse, said diode being .poled to discharge said capacitor through said switching transistor while said switching transistor is conductive; and

an electroacoustic transducer connected to said gate.

6. The combination according to claim 5, wherein said switching transistor is a PNP transistor having a grounded emitter and a collector normally maintained at a voltage negatively greater than said gating voltage.

.7. In a system for simulating banjo playing by means of an electronic musical instrument:

means for generating steady state tone signals; means responsive to each of said tone signals for providing at least two tone signal componentsof audibly different frequency content; Y

a control device;

means including percussive gating circuits responsive to said control device for shaping. said at least two tone signals to have substantially instantaneous and simultaneous buildups and relatively slow acoustically diverse decay rates immediately following the buildups, said decay rates differingby a factor of at least two; and

an electroacoustic transducer responsive to the shaped tone signals, said frequency contents and decay rates being selected to simulate the sound of a banjo.

8. The combinationaccording to ,claim 7, wherein said control device is a key switch and said electronic musical instrument is an electronic organ.

9. In a system for simulating playing tones by means of an electronic musical instrument:

means for generating plural steady state tone signals;

fingering devices for at will simultaneously connecting said tone signals to a common collector in response to selective actuation; and

means responsive to actuation of any of said fingering devices regardless 'of the actuated condition of the remainder of said fingering devices for converting all the tone signals on said common collector corresponding with all the actuated fingering devices to plural percussive tones having substantially instantaneous rise times and respectively audibly diverse decay rates.

10. A tone generating system for an electronic organ, which simulates the sound of a single strokeof a banjo, comprising:

a keyboard having an array of keys;

means responsive to actuation of any one or more of said keys for calling forth corresponding tone signals and for generating a gate trigger voltage; and means in separate channels for filtering and shaping said tone signals to simulate in one-of said channels a wave shape corresponding with the sound of the drum head of a banjo when strings are plucked, and in another of said channels the sound of said strings, said channels each including a separate percussive gate having a substantially instantaneous buildup and relatively slow decay times which are different by a factor of at least two for the separate percussive gates. I 11. The combination according to claim 10, wherein the time constants for said decay rates are about 30 ms. for said one of said channels and about 75 ms. for said another of said channels. H

12. The combination according to claim 11, wherein said means for filtering is a high pass filter for said one of said channels peaking at 1 kc. and is a high pass filter without peaking for said another of said filters. 13. in an electronic organ: a keyboard having keys; two distinct key switches closable in of each of said keys; a separate tone source pertaining to each of said keys; a source of DC current common to all said keys; a DC header; a tone signal header; means responsive to actuation of anyone of said keys for transferring tone signal from the tone source pertaining to that key to slid tone signal header and said DC current to said DC header; plural tone signal channels connected-in parallel to said one signal header, each of said tone signal channels including a separate tone forming filter and a normally nonconductive percussive gate; means responsive to each increase of-current on said DC header for actuating all said gates to become highly conresponse to actuation ductive substantially instantaneously and thereafter to effect decay of Conductivity of said gates at widely diverse rates; and

the rates of decay and the characteristics of the tone forming filter being selected to produce a sound simulating the sound of a percussive stringed instrument.

14. In an electronic organ:

a keyboard having an array of keys, each pertaining to a musical tone signal, a header;

means responsive to actuation of any one or combination of said keys alone and simultaneously despite minor time separations among the actuations of the separate keys of the combination of said keys or the then actuated condition of others of said keys for generating only one control pulse, means responsive to actuation of any combination of said keys for applying corresponding musical tone signals to said header while said keys remain actuated;

means for applying said musical tone signals to said header distinctively via separate channels; and

means responsive to said one control pulse for percussively an array of keys each pertaining to a tone signal source;

key switches operable by said keys each for connecting one of said tone signal sources to said common tone signal header;

a source of DC voltage; and

means for further connecting said source of DC voltage to said DC header via a high resistance in response to actuation of each of said keys, whereby current in said header is a function of the number of said keys which are actuated, a DC load connected between said header and ground, a first transistor, a second transistor, means biasing said first transistor normally conductive and said second transistor normally nonconductive, means including a capacitive coupling network for only transiently coupling said first transistor to become transiently nonconductive responsive to predetermined voltage changes occurring across said DC load, means including a further capacitive coupling network for only transiently coupling said second transistor to become transiently conductive responsive to transient nonconductivity of said first transistor, at least one normally nonconductive tone gate responsive to the transient conductive condition of said second transistor to become initially conductive in a predetennined temporal patternv during said transient nonconductivity and thereafter, gradually resuming its nonconductivity. 

1. An electronic organ, comprising: a source of tone signal; a key switch connected in cascade with said source; means responsive to closure of said key switch for generating a transient pulse; a percussive gate connected to said key switch, said percussive gate having a gate electrode; means normally applying a gating voltage to said gate electrode of magnitude and polarity adapted to maintain said gate nonconductive; a capacitor connected between said gate electrode and a point of reference potential; means responsive to said transient pulse for rapidly discharging said capacitor to said reference potential and thereafter for slowly charging said capacitor to said gating voltage; said reference level being sufficiently low to render said gate conductive; and an acoustic transducer connected in cascade with said gate.
 2. The combination according to claim 1, wherein said percussive gate is a field effect transistor.
 3. An electronic organ comprising: plural sources of tone signals providing a gamut of tone signals arranged in frequency according to a musical scale; a separate key switch connected in cascade with each of said sources; a common collector connected in cascade with all said tone sources; means responsive to closure of any of said key switches regardless of the then condition of the remainder of said key switches for generating a control pulse; plural gates connected in parallel with each other to said common collector, said gates being normally nonconductive; means responsive to said control pulse for rendering said gates rapidly conductive and thereafter relatively slowly conductive at audibly diverse rates for the separate gates; and an acoustic transducer connected in cascade with said gates.
 4. The combination according to claim 3, wherein is included a tone color filter in cascade with each of said gates, said tone color filters having diverse frequency response characteristics.
 5. An electronic organ, including: a source of tone signal; a percussive gate connected with said source of tone signal; a load for said gate, said gate including a gate electrode, a sustain capacitor connected between said gate electrode and a point of reference potential; a source of off gating voltage; a resistive circuit connected between said source of voltage and said gate electrode, said capacitor and resistive circuit having an audibly evident time constant; a normally nonconductive switching transistor; a normally nonconductive diode connecting said gate electrode to said transistor; a source of control pulse connected in control relation to said switching transistor, said switching transistor arranged to be rendered conductive in response to said control pulse, said diode being poled to discharge said capacitor through said switching transistor while said switching transistor is conductive; and an electroacoustic transducer connected to said gate.
 6. The combination according to claim 5, wherein said switching transistor is a PNP transistor having a grounded emitter and a collector normally maintained at a voltage negatively greater than said gating voltage.
 7. In a system for simulating banjo playing by means of an electronic musical instrument: means for generating steady state tone signals; means responsive to each of said tone signals for providing at least two tone signal components of audibly different frequency content; a control device; means including percussive gating circuits responsive to said control device for shaping said at least two tone signals to have substantially instantaneous and simultaneous buildups and relatively slow acoustically diverse decay rates immediately following the buildups, said decay rates differing by a factor of at least two; and an electroacoustic transducer responsive to the shaped tone signals, said frequency contents and decay rates being selected to simulate the sound of a banjo.
 8. The combination according to claim 7, wherein said control device is a key switch and said electronic musical instrument is an electronic organ.
 9. In a system for simulating playing tones by means of an electronic musical instrument: means for generating plural steady state tone signals; fingering devices for at will simultaneously connecting said tone signals to a common collector in response to selective actuation; and means responsive to actuation of any of said fingering devices regardless of the actuated condition of the remainder of said fingering devices for converting all the tone signals on said common collector corresponding with all the actuated fingering devices to plural percussive tones having substantially instantaneous rise times and respectively audibly diverse decay rates.
 10. A tone generating system for an electronic organ, which simulates the sound of a single stroke of a banjo, comprising: a keyboard having an array of keys; means responsive to actuation of any one or more of said keys for calling forth corresponding tone signals and for generating a gate trigger voltage; and means in separate channels for filtering and shaping said tone signals to simulate in one of said channels a wave shape corresponding with the sound of the drum head of a banjo when strings are plucked, and in another of said channels the sound of said strings, said channels each including a separate percussive gate having a substantially instantaneous buildup and relatively slow decay times which are different by a factor of at least two for the separate percussive gates.
 11. The combination according to claim 10, wherein the time constants for said decay rates are about 30 ms. for said one of said channels and about 75 ms. for said another of said channels.
 12. The combination according to claim 11, wherein said means for filtering is a high pass filter for said one of said channels peaking at 1 kc. and is a high pass filter without peaking for said another of said fIlters.
 13. In an electronic organ: a keyboard having keys; two distinct key switches closable in response to actuation of each of said keys; a separate tone source pertaining to each of said keys; a source of DC current common to all said keys; a DC header; a tone signal header; means responsive to actuation of any one of said keys for transferring tone signal from the tone source pertaining to that key to slid tone signal header and said DC current to said DC header; plural tone signal channels connected in parallel to said one signal header, each of said tone signal channels including a separate tone forming filter and a normally nonconductive percussive gate; means responsive to each increase of current on said DC header for actuating all said gates to become highly conductive substantially instantaneously and thereafter to effect decay of conductivity of said gates at widely diverse rates; and the rates of decay and the characteristics of the tone forming filter being selected to produce a sound simulating the sound of a percussive stringed instrument.
 14. In an electronic organ: a keyboard having an array of keys, each pertaining to a musical tone signal, a header; means responsive to actuation of any one or combination of said keys alone and simultaneously despite minor time separations among the actuations of the separate keys of the combination of said keys or the then actuated condition of others of said keys for generating only one control pulse, means responsive to actuation of any combination of said keys for applying corresponding musical tone signals to said header while said keys remain actuated; means for applying said musical tone signals to said header distinctively via separate channels; and means responsive to said one control pulse for percussively shaping the tone signals in said separate channels in wave shapes which are different for the separate channels but identically independent in each of said channels of the durations of actuations of said keys.
 15. In an electronic organ: a common tone signal header; a DC header; an array of keys each pertaining to a tone signal source; key switches operable by said keys each for connecting one of said tone signal sources to said common tone signal header; a source of DC voltage; and means for further connecting said source of DC voltage to said DC header via a high resistance in response to actuation of each of said keys, whereby current in said header is a function of the number of said keys which are actuated, a DC load connected between said header and ground, a first transistor, a second transistor, means biasing said first transistor normally conductive and said second transistor normally nonconductive, means including a capacitive coupling network for only transiently coupling said first transistor to become transiently nonconductive responsive to predetermined voltage changes occurring across said DC load, means including a further capacitive coupling network for only transiently coupling said second transistor to become transiently conductive responsive to transient nonconductivity of said first transistor, at least one normally nonconductive tone gate responsive to the transient conductive condition of said second transistor to become initially conductive in a predetermined temporal pattern during said transient nonconductivity and thereafter, gradually resuming its nonconductivity. 